US1841998A - Electric accumulator - Google Patents

Description

M. WILDERMAN ELECTRIC ACCUMULATOR Filed Oct. 31, 1929 Jan. 19, 1932.

INVENTOR Wa, A 2%.

Patented l Jan. 19, 1932 i PATENT OFFICE ELECTRIC ACCUMULATOR Application ledctober 3l', 1929. S'erial No. 403,898.

This invention relates to an electric accumulator and provides material improvements tion,

vlo

is on the regulates 1n the efficiency and utility thereof.

This application is a continuation in part of` my application Seria-1 No. 745,637, filed October 24, 1924.

The usual electric accumulator comprises spaced electrodes immersed in a solution of sulphuric acid. All chemical react-ions in the accumulator take place at the surface of conjtact between the sulphuric acid and the solid sponge lea-d and lead peroxide, as well as with the solid SOiPb which separates on the elecl trodes. During discharge of the battery the acid becomes more dilute and during charge more concentrated. The acid which surface of contact is the first to take partin the reaction so that during charge or discharge there is a condition of non-uniform acid density existing in the cell.\

becomes During discharge the more 'concentrated acid between the electrodes is supplied by diffusion tothe more dilute acid at the surface of contact with the electrodes, and in the pores of theactive material. In charging, the reverse condition exists, the more concentrated acid lying adjacent the electrodes and inthe pores of the active material, Diffusion is relatively a slow process and it cannot supply or remove the HZSO, to or from the electrodes with the same speed as it is removed by the current from thesoluor is increased in the same at'the surface of the electrodes and within the pores of the active material. Asa result of this', the voltage, and with it the ampere-hour and watt#l hour capacity drop considerably on account Y of the drop of acid concentration at theclectrodes during discharge, this drop being the greater the higher the current of discharge.

During charging the rate of diffusion again the rate of transportation of the HZSO.1 from the acid Within the pores and the surface of the electrodes to the acid layer therebetween so long as no gassing takes place in the cell. At 2.3 volts the cell begins to gas, separating hydrogen and oxygen which effectively stir the acid solution between the diaphragm and the electrodes making the density of the solution uniform. The

cumulator depends, including its speed of recuperation, can only-be'obtained, if the speed with which the vsulphuric acid of the total acid solution in the battery is brought to the surfaces ofthe electrodes is made to be greater than itis under. the action of diffusion.

vThis I achieve by the introduction of automatic' circulation of the solution between the electrodes under the action of charge and discharge.

I provide means whereby the hydrostatic and electro-osmotic pressures are employed for producing effective and automatic circulation and mixing of the electrolyte between the electrodesv so as to prevent the setting up ofthe conditions above described. To this end I employ a diaphragm having a rate of percolation materially greater than the wooden separators or threaded rubber separators now employed. I preferably employ a separator made of porous ebonite. These separators may be readily manufactured and their properties may be very accurately controlled. Their process of manufacture is fully set forth in my Patent No. 1,651,567 for process of manufacturing porous bodies, diahragms, filters and the like of-ebonite, dated ecember 6th, 1927.'

In order to 'fully enjoy the advantages of my inventlon a `number of conditions must be complied with, as follow a A diaphragm must be used as a separator in order that hydrostatic and electroosmotic pressures are created between the electrodes. 'lhis condition is not obtained by perforated sheets since no electro-osmotic they are used.

b The concentration of the electrolyte on the different sides of the diaphragm must be maintained of a different strength during lo' i charge and discharge as otherwise no hydrostatic pressure is obtainable, and the electroosmotlc pressure is materially diminished. In order to maintain this difference in concentration of electrolyte I so position the diaphragm that a greater quantity of electrolyte lies on one side of the plate than on the other. Preferably the diaphragm is placed so that it is closer to the negative electrode than to i and the electrodes are very small, usually one millimeter or less, the separators must be so constructed and be of such properties that the proper positioning of the diaphragm is maintained throughout the life of the battery. For this reason I provide the separators or diaphragms with a non-compressible frame or ribs capable of effectively counteracting the bending and buckling o the electrodes, the frame or ribs and the diaphrgm at the same time remaining unaffected by the electrode or by the gases evolved in the battery.

d While the separator should be placed closer to the negative than to the positive electrode, it is desirable to leave a free space at the negative side of the diaphragm between the diaphragm and the negative electrode so as to permit of circulation of the solution be- `as that of the earthenware tween the diaphragm and the electrode.

e The diaphragm must have a very high rate of percolation in order that the small values of the hydrostatic pressure and of the electro-osmotic pressure is suilicient for producing the desired results.

The speed of percolation of a porous diaphragm'depends upon the porosity and upon the radius of the capillarities in the diaphragm and only a great porosity and a suficient radius ofthe capillaries makes it possible to secure the desired speeds of percolation. By making separators as described in my patent above referred to, itis possible to secure diaphragms having remarkably high rates of percolation. For example, careful investigations extending over long periods and made with numerous samples, have shown that the speed of percolation through an ebonite diaphragm made of a powder of grain 0.9 millimeters and of about 50% porosity is from 40,000 to 100,000 times as great as that of Wooden diaphragms of the same thickness, about v8000 times as great diaphragms used in Leclanch cells and about 1000 times as w great as that of threaded rubber after the lsolution is on percolation of t latter have been in water or solution for a,

few days.

The above was established by direct measurements of the speed of percolation by the method of P. A. Guye, Journal de Chimie et de Physique, Vol. II, page 79 (1904) With a treated wooden separator 0.9 millimeter thick, about 20 cm2 surface, 0.14 cm3 passed per minute under the pressure of a column of solution 107 cm high, i. e. 0.000007 cm3 solution passed per cm2 of separator per minute and 1 mm pressure of solution.

With porous ebonite separators of the same dimensions 0.35 to 0.7 cm3 of solution passed per cm2 of the diaphragm per minute and 1 mm pressure of the solution.

The last can also be much simpler illustrated by bringing a drop of water on a porous ebonite separator; it passes instantaneously to the other side also when the thickness of the drop became 0.1 mm or even less.

The .thickness of the separators being usually about 0.9 or 1 mm the above data give also the exact amounts of solution which must pass the diaphragm, whenit is placed between the electrodes and an overpressure of 1 mm water alone exists, for one reason or another, from one side of the diaphragm to the other. If the distance between the diaphragm and the electrode be 1 mm the total vamount of solution per centimeter square of the diaphragm between the electrode and the separator is 0.1 cm3, that is, the solution between the separator and the electrode has been renovated 3, 5 to 7 times per minute, and if this distance is only 0.4 mm the solution between the diaphragm and the electrode has been renovated 9 to 18 times per minute. The pressure on the solution in any given capillary of the diaphragm being greater at the one end of the capillary than at the other, the same is bound to move in the capillary from the side of greater pressure to the side of the smaller pressure. ccording to the elementary laws of hydrostatics the total pressure on the solution in any such capillary of the diaphragm is at each end equal to the section of the capillary multiplied by the height of the column of the solutionfrom the capillary to the top surface of the solution in the cell multiplied by the average specific gravity of this column. If therefore for one reason or'another the specific gravities or the concentration of the both sides of the diaphragm different such a movement of the solution through the dia hragm is 4 inevitable however the cell may constructed, whether the separators and the electrodes are closed up in the cell or not, the amount of solution passing through the diaphragm depending besides the ove ressure upon the speed of e diaphragm. It is very great in case of a orous ebonite separator, and extremely sma l or practically zero for all practical purposes in case of a wooden separator. A

In the porous separator of great percola.

tion'the solution moving through the diaf phragm is doing this at the total surface of the electrode, not on one or two places of the electrode alone; and the distance between the two electrodes, as well as between the separator and the electrodes, being very small `a very small movement of the solution is sulicient to bring it mechanically up to the surfaces of the electrodes themselves. It is for this reason that I designate this as circulation of the .electrolyte between the electrodes, extending its activity up to the surfaces of the electrodes themselves where it is most needed.

To create such a difference of the concentration on both sides of the diaphragm in an automatic manner I place the diaphragm between the electrodes in such a manner that more solution is between the diaphragm and one of the electrodes than between the same asd the other. The object being to keep the concentration of the thicker layer of solution between the diaphragm and the electrode higher, when during discharge the same number of molecules of sulphuric acid disappear at each electrode.

If the separator is so placed between the electrodes that the amount of solution on each side ofthe separator is the same, the concentration of the solution during discharge will be on each side of it also the same and there will be no, or practically no, movement of the solution through the diaphragm, also when its speed of percolation is otherwise great. Similarly if the separator is placed with the one side straight on one of the electrodes (say the negative), so that no free space between the separator and the electrode is left, the circulation is mechanically prevented because the requisite free space for movement of the solution is not provided for. For this reason the separator must be so placed between the electrodes that there should be free space between the separator and each of them.

In a cell of a A. H. capacity, having 11 electrodes and 10 separators of say 13 cm X 15 cm, the total surface of the separator is about 2000 cm2 and the total surface of the capillaries of the separators having a 50% porosity through which the` solution is pressed is about 1000 cm2, which for a separator of greatspeed of percolation is enormous.

In the accompanying drawings given by way of example to illustrate the present invention,

Figure 'l is a separator,

Figure 2 is a plan view of a. slightly modified form of separator,

' Figure 3 is a cross ysection of the frame of plan view of one form of the separator on line III-III, if the frame is madeV of a nonporous substance such as ebonite,

Figure 4 is the cross section of tbe separator on line IV-IV, when the frame and the vertical strips are made of a nonporous substance such as nonporous ebonite, while the diaphragm consists of a porous substance such as porous ebonite,

Figure 5 gives the cross section of the same separator on the same line IV-IV of the frame, the vertical strips also consist of a porous substance such as porous ebonite.

Figure 6 is a horizontal section of a cell showlng the arrangements of the electrodes and thev separators between so placed as to give more solution at the positive electrodes than at the negative electrodes, v

Figure 7 is a vertical section of the same battery viewed from the narrow side of the battery on the line VII-VII .of Figure 6,

F ioure 8 gives a cross section of a separator Fig. 2 made wholly of a porous substance such as porous ebonite containing two vertical strips at the ends and small vertical strips between at eachside of the separator.

Referring to the drawings, the separator illustrated in Figures l, 3, 4,6 and 7 comprises a web portion 2 of say porous ebonite which isl completely surrounded by a frame 3 of nonporous ebonite. The web 2 is provided with spaced ribs 4 which contact with adjacent electrodes to maintain the separator spaced therefrom the web 2 being more reV moved from one electrode (in this case from the positive electrode) than from the other (in this case the negative electrode), the front surfaces of the frame and of the ribs being removed from the web more on one side than on the other (see cross section Figures 3, 4, as well as Figures 6 and 7). The top portion '5 and the bottom portion 6 of the frame 3' are provided with projections 7 which allow the gas to escape during 'charge of the cell. i

'Figure 5 shows the same Figure 4 if the separator is wholly made of porous ebonite` the front surfaces ofthe frame and of its projections 7 in the top and the vertica-l ribs 4 being more removed from the Surface of the web 2 on one side than on the other.

In the modified form of separator shown in Figure 2 and Figure 8, the wide ribs 3 andthe narrow ribs 4 as well as the web 2- are made of a porous substance such as ebonite. The ribs 4 and the vertical ribs 3 extending beyond the plane of the web on both sides, more on the one side than on the other, the separators being used with the electrodes in the battery and arranged in the same manand bottom portion ner as illustrated in Figures 6 and 7 g In this case the separator is shownto contain also ribs 8 between the ribs 4 on one side of the 9 as illustrated in fFigures 6 and 7. The frames 3 and the vertical ribs contactin with the adjacent electrodes prevent distortion of the electrodes which have a tendency to warp or buckle, especially at high rates of discharge. In Figure 7 the level of the electrolyte is indicated by the line lil-E. The cell is provided with a vent plug 10 which allows the gases developed inthe cell to escape.

In the embodiment shown in Figures 1, 3, 4, 5, 6, and 7 the frame 3 extends completely around the separator. --c

It should be understood that the present invention is not restricted tothe forms of separator given by way of illustration here, nor to the kind of material used for the porous separator, as long as the porous separator is of a great speed of percolation and the separator when used in connection with the electrodes .in the battery is removed from the active material of the one electrode more than from that of the other.

I claim: l. In an electric accumulator having spaced electrodes adapted vto be submerged in an electrolyte, a porous diaphragm having a j web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte.

2. In an electric accumulator having spaced electrodes adapted to be submerged in an electrolyte, a porous ebonite diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte.

3. In an electric accumulator having spaced electrodes adapted to be submerged .in an electrolyte, a porous diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode ythan from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the diaphragm having ribs which roject belyond the web more on one of its siv es than on the-other..

4. In Van electric accumulator havin spacedelectrodes adapted to be submerge in an electrolyte, a porous ebonite diaphragm having a web, the dia hragm'being of great f5 speed of percolation, ying betweenthe electrodes and Aacting as a separator, the diaphra contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side o the web for free circulation of the electrolyte, the diaphragm having ribs which project beyond the web more on one of its sides than on the other.

5. In an electric accumulator havin spaced electrodes adapted to be submerged in an electrolyte, a porous diaphragm having a web, the diaphragm being of great speed of percolation,'lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the web being surrounded by a frame which is thicker than the web and projects beyond the surface of the web on both sides, the projection on one side being greater than on the other.

6. In an electric accumulator having spaced electrodes adapted to be submerged in an electrolyte, a porous ebonite diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other one and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the' web being surrounded by a frame which is thicker than the web and projects beyond the surface of the web on both sides, the projection on one side being greater than on the other.

7. In an electric accumulator having spaced lelectrodes adapted to be submerged in au electrolyte, a porous diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting' as a separator, the diaphragm contacting with the ad]acent electrodes, the web of the diaphragm being more removed the other and forming unequal free spaces on\elzich side of the web for free circulation of t e electrolyte, the web being surrounded by a frame which is thicker than the web and projects beyond the surface of the web on both sides, the projection on one side being greater than on the other, and other ribs within the frame and of the same thickness as the frame.

8. In an electric accumulator havin spaced electrodesadapted to be submerge in an electrolyte, a porous ebonite diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diafrom one electrode than from phragin contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the web being surrounded by a frame which is thicker than the web and projects beyond the'surface of the web. on both sides, the projection on one side being greater than on the other, and other ribs within the frame and of the same thickness as the frame.

9. In an electric accumulator having spaced electrodes adapted to be submerged in an electrolyte, a porous diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, vthe diaphragm contacting with the adjacent electrodes, the web of the' diaphragm being more'V removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the diaphragm having nonporous ribs projecting beyond thelsurface of the web on both sides, the projection on one side being greater than on the other.

10. In an electric` accumula-tor having spaced electrodes adapted to be submerged in an electrolyte, a porous ebonite diaphragm having a web, the diaphragm being of great speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent elecf-rodes, the web of the diaphragm being more removed .from one electrode than from the other and forming unequal free spaces on Y each side of the web for free circulation of the electrolyte, the diaphragm having ribs of non-porous ebonite projecting beyond the surface of the web on both sides, the projection on one side being greater than on the other. A 11. In an electric accumulator havin-g spaced electrodes adapted to be submerged in an electrolyte. a porous diaphragm having a web, the diaphragm being of great Speed of percolation, lying between the electrodes and acting as a separator, th dia-v phragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free Aspaces on each side of the web for free circulationo the electrolyte, the web being surrounded by a frame which is thicker than the web and projects beyond the surface of the web on both sides, the projection on one side being greater than on the other, at least one of the horizontal portions of the frame being provided with channels for the escape of gas;

speed of percolation, lying between the electrodes and acting as a separator, the diaphragm contacting with the adjacent electrodes, the web of the diaphragm being more removed from one electrode than from the other and forming unequal free spaces on each side of the web for free circulation of the electrolyte, the web being surrounded by a frame which is thicker than the web and projects beyond the surface of the web on both sides, the projection on one side being greater than on the other, at least one of the horizontal portions of the frame being prol` vided with channels for the .escape of gas.

In testimony ywhereof I have hereunto set my hand.

ME YER VVILDERMAN.

12. In an electric accumulator having I

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